The carpal tunnel is a space in the palm region of a human hand. The floor of the carpal tunnel is formed by a concave arch of carpal bones that are covered by wrist ligaments. The roof of the carpal tunnel is formed by the transverse carpal ligament extending in the transverse direction across the wrist from the base of the thumb to the outer portion of the wrist bones. The carpal tunnel forms a conduit for the median nerve (which innervates portions of the index, middle and ring fingers, and the thumb) and nine digital flexor tendons (which control finger movement) extending from the forearm into the palm.
Carpal tunnel syndrome is a condition where the median nerve is compressed within the carpal tunnel, resulting in pain and/or numbness in the wrist and/or hand. Compression of the median nerve can result from a reduction in the size of the carpal tunnel, an increase in the volume of the tissue inside the carpal tunnel, or by movement of the flexor tendons. Compression of the median nerve can cause pain, numbness or a prickly, tingling sensation in the wrist, hand, fingers or thumb that can radiate to the forearm.
A surgical technique for relieving pressure within the carpal tunnel includes bisecting the transverse carpal ligament that forms the roof of a carpal tunnel. Once the transverse carpal ligament is cut, the pressure within the carpal tunnel is relieved and the pain, numbness and/or tingling caused by compression of the median nerve is reduced or eliminated.
The transverse carpal ligament is generally cut in a direction transverse to the ligament, which is approximately along a line drawn from the patient's elbow to the patient's fingers. Along the direction of the cut, the thickness of the transverse carpal ligament is not constant. The transverse carpal ligament is thinnest on the proximal side (side nearest the elbow) and thickest on the distal side (side nearest the fingers). Schematic diagrams of the transverse carpal ligament and the carpal tunnel are illustrated in prior U.S. patents, such as U.S. Pat. Nos. 5,507,800 and 6,179,852, the disclosure of which is incorporated by reference.
In bisecting the transverse carpal ligament, a surgeon must take care to avoid damaging the median nerve and other vital tissue extending beneath the transverse carpal ligament. Damaging the median nerve can result in long-term pain or limited mobility. Although no nerves overlie the transverse carpal ligament, cutting the tissue above the transverse carpal ligament increases short-term pain and recovery time following an operation. Despite these disadvantages, surgeons cut the tissue overlying the transverse carpal ligament during carpal tunnel release surgery.
It was realized by the inventor of the current invention that improvements in tools for bisecting the transverse carpal ligament are needed. For example, it was realized that improvements in guides for bisecting the transverse carpal ligament that avoid damage to the median nerve and minimize damage to the tissue overlying the transverse carpal ligament are needed.
Certain preferred features of the present invention address these and other needs and provide other important advantages. Some or all of these features may be present in the corresponding independent or dependent claims, but should not be construed to be a limitation unless expressly recited in a particular claim.